[rm-all-el-array] remove all elements from an array (#17351)

Author: sk1418

core-java-modules/core-java-arrays-operations-basic-2/src/test/java/com/baeldung/array/removeallelements/RemoveAllElementsFromStringArrayUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.array.removeallelements;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Test;
+
+public class RemoveAllElementsFromStringArrayUnitTest {
+
+    private static final String[] SIX_NULL_ARRAY = new String[] { null, null, null, null, null, null };
+
+    @Test
+    void whenReassignNonFinalArray_thenCorrect() {
+        String[] myArray1 = new String[] { "Java", "Kotlin", "Ruby", "Go", "C#", "C++" };
+        myArray1 = new String[0];
+        assertEquals(0, myArray1.length);
+
+        String[] myArray2 = new String[] { "Arch Linux", "Debian", "CentOS", "Gentoo", "Fedora", "Redhat" };
+        myArray2 = new String[myArray2.length];
+        assertArrayEquals(SIX_NULL_ARRAY, myArray2);
+    }
+
+    @Test
+    void whenResettingAllElementsToNull_thenCorrect() {
+        final String[] myArray = new String[] { "A", "B", "C", "D", "E", "F" };
+        for (int i = 0; i < myArray.length; i++) {
+            myArray[i] = null;
+        }
+        assertArrayEquals(SIX_NULL_ARRAY, myArray);
+    }
+
+    @Test
+    void whenUsingArraysFill_thenCorrect() {
+        final String[] myArray = new String[] { "a", "b", "c", "d", "e", "f" };
+        Arrays.fill(myArray, null);
+        assertArrayEquals(SIX_NULL_ARRAY, myArray);
+    }
+}